Cosmology

Astronomers think that there are at least several billion galaxies in
the Universe. The exact number is not known.
This is based on observations of how many galaxies we see in a small
part of the sky scaled to give us an estimation of how many galaxies
there would be in the whole sky.

What is temperature of the cosmic background?

The cosmic background temperature (which peaks in the microwave) is about
2.7 degrees Kelvin.

Do astronomers have to look into one direction of the sky to see back in time?
Where did the Big Bang happen?

Astronomers do not have to look towards a specific location to peer back in
time. They can peer back in time by looking in any direction in space.
Everything in space is moving away from us because the Universe is expanding.
The Big Bang did not occur at one single point in space, it occurred at all
points in space because, according to the theory, the Big Bang created space
itself. So far, astronomical observations support this. We can detect the
degree Kelvin background radiation left over
from the Big Bang in all
directions in space. Also, galaxies in all directions of space are moving
away from us and each other.

What is a quasar?

Quasars (quas[istell]ar objects) are believed to be the most remote objects in the universe.
Despite their small size they produce tremendous amounts of light and microwave radiation: not
much bigger than Earth's solar system, they pour out 100 to 1,000 times as much light as an entire
galaxy containing a hundred billion stars.